Microphone



Feb. 25, 1930.- s. RUBEN 1,748,620

MICROPHONE Filed-ost. 15. 1928 FIG.2.

anw/nto@ SAMUEL /UBE/V mi m www WQWM Patented Feb. 525, 1930 UNITED STATES PATENT OFFICE SAMUEL RUBEN, OF NEW YORK, N. Y., ASSIGNOR TO RUBEN PATENTS COMPANY, OF NEW YORK, N. Y.,YA CORPORATION OF DELAWARE MICROPHONE I Application'led October 15, 1928. Serial No. 312,683.

sensitivity and which is durable and low in 1U cost of construction.

I have found that the contact resistance of cuprous oxide sensitively varies with the pressure applied to its surface and that this 1raterial can be used particularly advantageous- 15 ly in an electric circuit to modulate a current when sound waves are impressed upon a contacting electrode, also in producing audio frequency oscillations in a circuit inductively related to a microphone employing an elec- 20 trode coated with cuprous oxide and connected in a. direct current circuit.

It is desirable to have a wide contacting surface area between the electrodes, the applied physical energy effecting substantially no change of contacting area but varying the inter-molecular contact at the junction between one electrode and another having the cuprous oxide layer, and causing a change in contact resistance of this material. For effective operation the oxide coating must be of a homogeneous, non-porous, dense, crystalline character integrally formed with the base material.

For a better understanding of this invention reference is made to the accompanying drawings in which Fig. 1 represents a graph of the electrical relation between the pressure applied to and the contact resistance of an electrode composed of copper with the cuprous oxide layer contacting with another electrode. Fig. 2 shows one embodiment of the invention in the formf amicrophone hav'- ing an electrode composed of a copper base with a layer of cuprous oxide contacting with another electrode. Fig. 3 shows the same microphonic arrangement connected with an electromagnet. Fig. 4 outlines a circuit in whichthis latter device is connected.

Referring more particularly to Fig. 2, 1 represents a steel diaphragm as one electrode,

2 a stationary copper electrode the surface of which is composed of a layer of fused cuprous oxide 3, electrode 1 andthe cuprous oxk'ide electrode being in Contact over the entire adjacent surface area vof the latter. These elements are enclosed in and supported by insulating vmembers 5 and 6. The copper electrode 2 is mounted on screw 4 supported in insulation member 6. A metal case 9 is used for encasing the several elements and the terminals of the two electrodes are respectively at 7 and 8.

In the arrangement shown in Fig. 3 a microphone is arranged to continuously produce electrical oscillations of audio frequency from a direct current.- On the side of diaphragm l, opposite that of the cuprous oxide layer 3, is arranged an electromagnet which can influence the position of steel diaphragm 1. The primary and secondary windings of the electromagnet are represented respectively at 10 and 11, the primary being connected to diaphragm 1 by leadv la and to the insulated electrode terminal 7 in the direct current supply circuit. The secondary winding is connec to twoinsulated terminals, 11a and 11b. In Fig. 4, G' represents a direct current generator.

In operation of the microphone as shown in Fig. 2, the initial resistance ofthe device is the sum of the contact and internal resistances; but as pressure is applied to the contact area, the resistance at the juncture between diaphragm 1 and the cuprous oxide layer 3 decreases, permitting a corresponding increase of current iow thro-ugh the device.

In the operation of the device as shown in Fig. 3, as direct current is applied to the terminals 7 and 8, current flows through the contact between the electrodes 1 and 2, land the electromagnetic primary coil 10. As this coil is energized diaphragm 1 is drawn toward the electromagnet, thereby reducing the pressure between the diaphragm 1 and the cuprous oxide layer 3, and increasing the 95 contact4 resistance to the flow of current through this circuit, causing a decrease in the direct current flow. The effect of such decreased current flow is that the diaphragm by lits spring pressure returns to its close con- @edit ico tact with surface 3, thereby increasing the contact pressure between the diaphragm and "the oxide surface and again permitting an c' increased flow through the direct current circuit. This cycle of action is continuously maintained, thereby producing a vibratory .movement of the diaphragm of` audio frequency. By reason of the'eld changes in the primary, there is induced in the secondary winding a potential of the frequency maintained by the oscillating diaphragm. Used as waves, and means for oscillating the vibratory/electrode by impressing thereon audio frequency oscillations from an electromagnet.

In testimony whereof, SAMUEL RUBEN has signed his name to this specification this 8th day of October 1928.

SAMUEL RUBEN.

an oscillator, power of'considerable magni- I tude and frequency, as in the order of 1000 cycles, has been maintained without difficulty over long periods.

With a disc electrode, having a contact area with a fused cuprous oxide electrode of .5"square inches and initially in complete surface contact therewith, the resistance change with pressure from 0 to 100 pounds was from 15,000 to 50 ohms.

Microphones constructed as here described show a sensitivity well beyond that of any of the devices known in the prior art; they are capable of modulating powers of much greater values without the limitations due to thermal effects, as commonly experienced in the carbon type of microphone.

What I claim is:

1. A microphone having as one of its pressure operative electrodes a copper body having on its surface a layer of a homogeneous,

'nonporous, dense, crystalline compound of lc)opper integrally formed with the copper ody.

2. A device for translating audio frequency oscillations into oscillations of like frequencies in an electric circuit, which comprises a vibratory electrode, in surface contact with a cuprous oxide cooperating electrode, means for directing audio frequency oscillations upon one of said electrodes and means for supporting and protecting said electrodes from extraneous audio frequency oscillations.

3. A device for translating sound Waves into oscillations of like frequencies in an electric circuit, lwhich comprises a vibratory electro'de, in surface contact with a puprous oxide cooperating electrode, means Yfor directing sound waves upon the first mentioned electrode, means for supporting and protecting said elements from extraneous sound waves and means for oscillating the vibratory electrode by impressing thereon audio frequency oscillations from an electromagnet, the energizing current for said device being controlled by the movement of said vibratory electrode. V

4. A device for translatingsound waves into electrical oscillations of like frequencies, which comprises a vibratory electrode in surface contact with a cooperating cuprous oxide electrode, means for supporting and shielding said electrodes from lextraneous sound 

